It is often desirable to display off of the visor of a helmet an optical image. This is generally useful for applications such as flight borne helmets where the viewer (e.g. a pilot) desires to see pictures or symbols reflected off the visor.
Reference is now made to FIG. 1A describing a typical helmet-mounted, prior art optical system involving a visor. The helmet typically comprises an image source 30 and relay optics 10. A picture is relayed from source 30, through Relay Optics 10, reflected off a visor 15 or combiner element, and into the viewer's eye 16, such as a pilot. In a typical system that establishes a conforming head wearing unit, the field of view (FOV) received by the user is limited due to both limited eye relief and limited optics diameter. Typically a reduced FOV of 30° to 40° is achieved, as could be seen in FIG. 1B. FIG. 1B is a graph published in the article “Head Mounted Displays” By Jams E. Melzer & Kirk Mofftt (ISBN 0-07-041819-5) that presents the FOV as a function of the eye relief and the optics diameter. According to the graph of FIG. 1B it can easily be seen that for eye relief of 20 mm and optics diameter of 20 mm the FOV is approximately 35 degrees. It is obvious that with airborne systems the eye relief and the optics diameter are tightly limited. Furthermore the actual FOV is even lower due to aberrations introduced by the visor shape. Increasing the FOV with the present art requires a substantial reduction in resolution and a substantially larger and heavier relay optics and helmet. As an example, in order to enlarge the FOV to 60°, the relay optics must be heavier than the one used for a FOV of 40°.